Air drain valve



June 30, 1936.

E. WIEDMANN ET AL AIR DRAIN VALVE "Filed Aug. 4, 1930 gmxvnl oz dttouwq Patented June 3%, lhfid AER DRAM Ernst Wiedmann and .lames K. Douglas, hillwaukee, Wis, assignors to The Oilgear ilompany, Milwaukee, Win, a corporation oi Wiscousin Application August 4, 1939, Serial No. 472,929 10 Claims. (c1. 251-=-1l-il This invention relates to air drains for draining entrapped air or gases from hydraulic circuits.

The air drain .to which the invention applies in particular has a restricted passageway, such as a coil of small diameter tubing, through which limited Volumes of liquid and air and other gases are forced by hydraulic pressure, and a valve for controlling this passageway to prevent air from entering the circuit when the liquid therein is not under pressure.

The invention is particularly adapted for use in hydraulic circuits in which the hydraulic pressure varies through a wide range, such as the circuits of hydraulically operated machine tools which carry a low pressure when the machine is running idle, a higher pressure when the. tool carriage is being operated at rapid traverse speeds and, usually, a still higher pressure when the cutting tool is being fed into or against a piece of work.

If the prior air drains were adjusted to pass the necessary volume of fluid at the low pressures to free a. circuit from entrapped air, so large a volume of liquid would escape when the air drain was subjected to a high feeding pressure that the efilciency and control of the machine were seriously affected.

If the passageways in the prior air drains were restricted suinciently to adequately restrain the discharge of liquid at high pressure, they would become clogged with foreign matter and, if the passageways. were large enough to minimize the danger of clogging, they had to be so-long that the resultant air drain was large and cumbersome. In any case, the continuous leakage through the air drain during the feeding operation detractedfrom the accuracy of the feed.

The present invention has as an object to provide an air drain valve which when connected to a hydraulic circuit will permit entrapped air or gas to escape therefrom without affecting the rate of operation of a hydraulic motor connected into that circuit.

Another object is to provide an air drain valve which is fully automatic in operation.

Another object is to provide an air, drain valve which is compact and emcient.

According to the invention in its general aspect and as ordinarily embodied in practice, the .air

drain valve is provided with a casing having an inlet which may be connected to a hydraulic circuit to permit liquid to escape therefrom into the casing'and an outlet through which liquid may escape from the casing, the inlet is connected to the outlet through a restricted passage through which liquid may flow at a predetermined limited rate at a predetermined low fluid pressure, a plunger is fitted in the casing and coacts therewith to close communication between the inlet and the outlet in either of two positions, the plunger is urged toward the inlet and into its initial position by a spring or other force in which initial position of the plunger communication between the inlet and the passage is kept closed until there is created in the circuit a predetermined low\ fluid pressure which overcomes the initial resistance of the spring or other force and moves the plunger out of its initial position to permit liquid to flow through the passage at a limited rate.

The liquid may continue to flow through the passage at the limited rate until either thepressure in the circuit drops sumcientiy to permit the spring or other force to return the plunger to its initial position and close the inlet to the restricted passage to prevent air from entering the circuit or until there is created in the circuit e.- pressure which' is enough higher than the low pressure to move the plunger farther from the inlet and into a position to again close communication between the inlet and the outlet and thereby prevent liquid from escaping from the circuit through the air drain valve at the higher pressure.

The invention is exemplified by the air drain valve illustrated in the accompanying drawing in which the views are as follows:

Fig. l is a central vertical section showing the valve closed to prevent the admission of air into a hydraulic circuit.

Fig. 2 is in part an elevation and in part a central section showing the valve closed to prevent the escape of fluid from a hydraulic circuit.

The air drain valve has a casing which, preferably, is formed of a cylinder l having a longitudinal bore 2, a head or cap 3 for closing the upper end of bore 2 and having an outlet e communicating therewith, and a plug 5 for closing the lower end of the bore 2 and having an inlet 6 communieating with the bore.

The head 3 and the plug 5 are connected to the cylinder 8 to make an oil tight seal therewith, as by the head 3 being threaded into the upper end of the bore 2 and provided with a shoulder i to abut the end of the cylinder l, and the plug 5 being threaded on the lower end of the-cylinder i into engagement with a shoulder 8 formed thereon.

The cylinder i contains a plunger 9 which is slidably fitted in the bore 2 andv provided upon its periphery with a spiral groove it through which limited volumes of liquid and air or other gas may pass from the inlet 6 to the outlet 4.

The groove l ordinarily extends around the plunger 9 throughout the greater part of the length thereof, to provide a long restricted passage through which liquid may flow only at limited rates, but it stops at a point short of the lower end of the plunger to provide an ungrooved portion which coacts with the wall of the bore 2 to close communication between the inlet and the outlet when the plunger is raised a sufficient distance, as shown in Fig. 2. The ungrooved por.- tion of the plunger thus functions as a valve for controlling the escape of liquid through the outlet 4 from any hydraulic circuit to which the air drain valve may be connected.

The bore 2 is enlarged at its lower end, as shown groove HI communicates when the plunger is in a lower position. Liquid may flow from the inlet through the counterbore into the groove and out of the groove into the outlet from the time that the plunger is raised slightly from the position shown in Fig. 1 until the ungrooved portion extends above the counterbore as shown in Fig. 2.

The flow of fluid from the bore 2 into the outlet 4 is secondarily controlled by a valve I I which is carried by the upper end of the plunger 9 and adapted to engage a valve-seat I! which is arranged upon the inner end of the head 3 and surrounds the outlet 4.

The flow of fluid from the bore 2 into the inlet 6 is controlled by a valve [3 which is carried by the lower end of the plunger 9 and adapted to engage a valve seat I 4 which is arranged upon .the inner surface of the plug 5 and surrounds the compression spring i5 which has its lower part arranged in a bore l6 formed in the plunger 9 and its upper part extended into the head 3 into engagement with'a washer I'I arranged therein.

The air drain valve is ordinarily connected into a hydraulic circuit at a high point therein and is provided upon the lower end of the plug 3 with threads I8 for engagement with the thread of a pipe fitting i9 or other part of a hydraulic circuit.

when a predetermined low pressure has been created in a hydraulic circuit to which the air drain is attached, liquid will enter the inlet 6 and exert suflicient force upon the bottom of the plunger 9 to raise it against the resistance of the spring i5 and thereby open the valve ll.

As air or other gas entrapped in a hydraulic circuit will work its way to the high points in the circuit, the liquid entering the air drain valve will carry entrapped air or other gas with it, and limited volumes of liquid and entrapped air or gas will flow through the groove l0 and escape through the outlet 4.

An increase in the pressure in the hydraulic circuit causes an increase in the rate of flow through the groove l0 which is sufficiently-large in diameter to avoid practically all danger of clogging and of suflicient length to provide the resistance required to limit the volume of escaping liquid to a predetermined maximum, for instance, 20 cu. in. per minute under a pressure of 125 pounds per square inch in the hydraulic circuit. In actual practice, the cross-sectional area of thegrcove iii does not exceed .012 sq. in.

An increase in pressure in the hydraulic circuit siso causes the plunger 9 to rise and thereby increase the resistance of the spring I! whichhoids the vaive open until the pressure reaches a predetermined maximum and then the ungrooved portion of the plunger 9 enters the unenlarged part of the bore 2 and prevents further escape of liquid through the groove III. A further rise in pressure will cause the valve I i to close and there- 5 by provide a second seal between the inlet and the outlet.

When the pressure in the circuit falls suiilciently, the spring l5 urges the valve iii to its seat to prevent air from entering the circuit 10 through the air drain valve.

The plunger 9 is thus reciprocated as the pressure rises and falls in the circuit to which the air drain valve is attached and thereby causes relative movement between the several turns of the groove l0 and the wall of the bore 2.

Particles of foreign matter carried by the liquid in the groove ID are thus rubbed against the wall of the bore 2 and either broken up or rolled along the groove in, thus allowing a smaller passageway to be employed than if the parts forming the passageway were wholly stationary.

The tension of the spring l5 may be varied in accordance with the requirements of the hydraulic circuit in which the air drain is to be employed, but it is found in practice that the circuits of practically all types of hydraulically operated machine tools are freed from entrapped air by employing an air drain valve having a spring it which will keep the groove I!) open until the pressure in the circuit reaches from '75 to 125 pounds per square inch and then allow it to be closed, and which will close the valve 13 when the pressure in the hydraulic circuit falls below flve pounds per square inch.

Entrapped air may thus drain from the circuit during the entire period that the machine is running idle and, in many circuits, during the time that the machine is operated at rapid traverse speeds but the escape of relatively large volumes (0 of liquid is effectively prevented when the circuit is carrying high feeding pressures, thereby freeing the circuit from entrapped air without aiiecting the e'fliciency of the control of the machine.

The invention herein set forth is susceptible of various modifications and adaptations without departing from the scope thereof as hereafter claimed.

' The invention is hereby claimed as follows:

1. An air' drain valve, for connection into a hydraulic circuit to enable entrapped air and gas to escape therefrom, comprising a casing. a plunger arranged in said casing and having a spiral groove arranged upon its periphery and providing with said casing a restricted passageway for the 55 passage of limited volumes of fluid through said casing, said groove having a cross-sectional area not exceeding .012 square inch, a valve carried by said plunger and adapted to be urged to its seat by fluid pressure in said casing, means re- 59 sisting the'action of said pressure and holding said valve open to enable limited volumes of fluid to pass'through' said casing in one direction until said pressure reaches a predetermined maximum and overcomes the resistance of said means and forces said valve to its seat to interrupt the passage of fluid through said casing, and another valve carried by said plunger for preventing the passage of fluid through said casing in the opposite direction and adapted to be held closed by said means until a predetermined low pressure has been created in said casing.

2. An air drain valve, for connection into a hydraulic circuit to enable entrapped air and gas to escape therefrom, comprising a casing having accuses I? a bore and an inlet thereto and an outlet therefrom, a plunger arranged in said bore to control said inlet and said outlet and having a spiral roove formed in its periphery and providing with the wall of said bore a restricted passageway for the passage of limited volumes or fluids through said bore, said groove having a cross-sectional area notexceeding .012 square inch, means for connecting said inlet to a hydraulic circuit to subject said plunger to the fluid pressure in said circuit and cause the same to be moved in said ing a bore and an inlet thereto and an outlet thcre- I from, a plunger arranged in said bore and having a spiral groove formed in its periphery to provide a restricted passageway through said casing, said groove having a cross-sectional area not exceeding .012 square inch, an inlet valve carried by said plunger for controlling said inlet, an outlet valve carried by said plunger for controlling said outlet, means carried by said casing for connecting said inlet into a hydraulic circuit to enable the fluid pressure therein to force limited volumes of fluids through said passageway and to urge said plunger toward said outlet to open said inlet valve and to close said outlet valve, and a spring urging said plunger toward said inlet to hold said inlet valve closed until a predetermined low pressure has been created in said circuit and to hold said outlet valve open until the pressure acting upon said plunger reaches a predetermined maximum.

4. An air drain valve, comprising a casing hav ing means for connecting it to a hydraulic circuit,

means providing a restricted passageway of con stant capacity for the discharge of limited vol= nines of fluid from said circuit to an exhaust, said passageway having a cross-sectional area not exceeding .012 square inch, a valve normally closing said passageway to said circuit and responsive to a predetermined low pressure in said circuit ior opening said passageway, and another valve responsive toa predetermined high pressure in said circuit for closingsaid passageway to the exhaust after ltih'as been opened to said circuit by said first named valve.

5. air drain valve, for connection into a hydraulic circuit to enable entrapped air and gas to-escape therefrom, comprising a casing having an inlet and an outlet, means providing between said inlet and said outlet an elongated restricted passageway not'exceeding .012 square inch in cross-sectional area and of a length sufficient to limit the flow therethrough to a predetermined low rate at a. given pressure, a valve arranged within said casing for controlling the flow of fluid through said passageway, a spring urging said valve to a position to close communication between said inlet'and said passageway, said valve member being responsive to a predetermined low pressure to open communication between said inlet and said passageway against the resistance of said spring, and a second valve connected to the first named valve and responsive to a predetermined. high pressure to close communication between said outlet and said passageway against further resistance of said spring.

6. An air drain valve, for connection into a by draulic circuit to enable entrapped air and gas to escape therefrom, comprising a casing having an inlet and an outlet, means providing between said inlet and said outlet an elongated restricteds passageway not exceeding .012 square inch in cross-sectional area and of a length sumcient to limit the flow therethrough to a predetermined low rate at a given pressure, a valve arranged 'within said casing for controlling the flow of fluid through said passageway, a spring urging said valve to a position to close communication between said passageway and said inlet, said valve being responsive to a predetermined low pressure to open said inlet to said passageway against the resistance oi. said spring, and a second valve con: nected to the first named valve and responsive to a predeterminedhigh pressure to close said outlet to said passageway against further resist ance of said ring.

7. An air drain valve, for connection into a lilydraulic circuit to enable entrapped air and gas to escape therefrom, comprising a casing having a bore and an inlet thereto and an outlet therefrom, a valve member fitted in said here and adapted to be subjected to the pressure at said inlet and having a spiral groove arranged in its periphery and forming with the wail of said bore a restricted spiral passageway for connecting said inlet and said outlet, said passageway having a length suficient to limit the flow therethrough to a predetermined low rate at a given low pressure, means for connecting said casing to a hydraulic circuit with said inlet in communication V therewith, said valve member controlling said in- 35 lot and said outlet and communication between said inlet and said groove, a'spring urging said valve member toward said inlet to close the same and adapted to permit said valve member to open said inlet in response to a predetermined low pressure in said circuit and to close communication between said inlet and said passageway in response to a predetermined high pressure in said circuit and to close said outlet in response to a higher pressure in said circuit.

8. An air drain valve, for connection into a hydraulic circuit to enable entrapped air and gas to escape therefrom, comprising a casing having a cylindrical bore and an inlet thereto and an.

outlet therefrom, means providing between said 50 inlet and said outlet a restricted passageway of a length sumcient to limit the flow therethrough to a predetermined low rate at a given pressure,

spring in response to a predeterminedhigh. presas A sure. r

9. An air drain valve, for connection into a hydraulic circuit to enable entrapped air and gas to escape therefrom, comprising a casing having a cylindrical bore and an inlet thereto and an out- 70 let therefrom, a valve member fitted in said bore and having as'piral groove formed in its periphcry to provide with the wall of said bore a restricted passageway of a length ,suflicient to limit the flow therethrough to a predetermined low rate 1| at a given pressure, a valve carried by said'vaive member for closing said inlet, a second valve carried by said valve member and coacting with the wall of said cylindrical bore for closing the inlet end of said passageway, and a spring urging said valve member to a position to close said inlet, said valve member being responsive to a predetermined low pressure to open said inlet to the inlet end of said passageway against the resistance of said 4 amazes spring and responsive to a predetermined high pressure to close said inlet end or said passageway against further resistance of said spring.

10. An air drain valve according to claim 8 further characterized by a third valve connected to the other two valves and responsive to a higher pressure for closing said outlet.

mus-r WIEDMANN. JAMES K. nouams. 

